KR20130108165A - Helicopter skid type landing gear - Google Patents

Abstract

The present invention relates to a helicopter having a fuselage and a skid-type landing gear mounted to the fuselage. The pivotable cross beams and skids, each of which are arranged to traverse essentially laterally on each side of the landing gear of the helicopter. At least one individual damper is provided with respect to at least one rotatable cross beam, the individual damper having one end connected to the pivotable cross beam and another end connected to the fuselage. The pivotable cross beam is of the cantilever type. Fixed and floating bearings are provided in the fuselage. Torsion bar springs are mounted to the fixed bearings and the floating bearings, wherein each respective inner end of the at least one pivotable cantilever cross beam is adapted for each of the pivotable cantilever cross beams in the fixed bearing. From the inner end, it is attached to the torsion bar spring in the floating bearing in such a way that moments are moved to the body via the torsion bar spring.

Description

Helicopter Skid Type Landing Gear

The present invention relates to a helicopter with a skid type landing gear with the features of the preamble of claim 1.

The landing gears of the helicopters must be designed to allow absorption of the vertical energy of the landing, by plastic deformation during hard landing and elastic deformation during regular landing. For example, in the case of a helicopter type with a conventional skid-type landing gear with cross tubes forward and backward, the respective plastic deformations can be up to 360 mm in the vertical direction in the rear cross tube and up to 460 mm in the front cross tube. Can be reached.

The landing gear of the helicopter can contribute to the so-called ground resonance phenomenon. In particular, the stiffness and damping properties of the landing gear affect the ground resonance. Ground resonance is a dangerous condition that can occur whenever a helicopter or gyroplane rotor spins while the aircraft is on the ground.

Ground resonance

Irregular spacing between blades of a rotorcraft

Damping of the damping system, fuselage and landing gear, as well as lead lag damping on the rotor when operating beyond the limits

Can happen.

With respect to skid type landing gear assemblies, two physical properties are of particular importance: one is vertical stiffness and the other is longitudinal stiffness. As used herein, the term "vertical stiffness" or "longitudinal stiffness" refers only to the linear or elastic portion of the load for stroke curves, which is the curve This is because the skid gears function during normal helicopter operation in the linear or elastic portion of the plane. Vertical stiffness is important for damping landing energy. The longitudinal stiffness is important because it is the primary source of frequency response to the ground resonance frequency. The damping behavior of the skid landing gear with two skid tubes and two cross tubes

Friction of the skid tubes on the ground caused by any vertical movement as a result of the vertical stiffness resulting in lateral movement of the skid.

Friction between the single parts of the landing gear assembly at the bolted joint and / or riveted joint.

Is affected by the hysteresis of any elastic components at the landing gear assembly or landing gear attachment points.

To change the damping of the fuselage, to change the damping of the rotor, or to change the characteristics of the landing gear, there are three common ways to eliminate ground resonance.

The most economical way to solve the ground resonance problem is to change the stiffness and damping behavior of the skid type landing gear, so that no ground resonance occurs. This can be done by adding some oblique struts between the components of the skid type landing gears at the expense of weight and traction. Certain cross-sectional shapes and materials of cross tube members can affect the stiffness. This is a viable approach, but not the most square. Sometimes, damping elements are added to the cross tube if the deflection of the tube allows for effective damping at a certain point.

Document US5224669A (Guimbal) discloses the use of dampers to control resonance.

Document US4196878A (Aerospatiale) discloses a landing gear for a rotorcraft aircraft having two main skids connected to an aircraft structure by two cantilevered arch supports. Each skid has at least one flexible element that can flexibly bend upon contact with the ground.

Document US4270711A discloses a helicopter landing gear assembly comprising a pair of cross tubes having a pair of struts connected at an outer end.

Documents US2010 / 0237190A and US2007 / 0181744A (Eurocopter) disclose a takeoff and landing device with fall arrest and anti-resonant skids for a rotorcraft.

Document US6427942A (Bell) discloses a skid landing gear for a helicopter, in which case the directional stiffness of the cross members of the skid landing gear is separated from each other so that the longitudinal stiffness of the cross members is independent of the vertical stiffness and the fatigue life of the cross members. Can be. To separate the stiffness in the skid type landing gear, two approaches are used. In the first approach, to separate the vertical stiffness of the cross members from the longitudinal stiffness, the skid landing gear in the cross section has a distribution of different materials and / or asymmetric section cross members. In the second approach, mounting devices that provide compliance in selected directions are used to separate directional stiffness.

The document US2011 / 0133378A (Nanokas Aviation) discloses a landing gear damper that allows proper ground resonant operation while reducing the need to maintain and reinforce the work with a spring and damper element coupled with the disc springs inside the damper cylinder. . The only drawback is that in the case of a fall landing, both of these combinations lead to high spot forces. Proper hard landing can deform the cross tubes to some extent. As a result, the cross tubes need to be replaced regularly, causing customer dissatisfaction. Cross tubes of skid-type landing gears in state-of-the-art helicopters operating on ships need to be replaced very often, as they soon reach the limits of the setting. The design of state-of-the-art skid type landing gears requires experience / analysis and trial and error to find the correct stiffness and requires damping to avoid ground resonances under all possible landing flight attitudes.

Document US3144223A (Nichols) discloses a skid type landing gear comprising cross beams each arranged essentially transverse to the longitudinal main axis of the helicopter, in which case the skids of the landing gear are flanked by the cross beams. Mounted at the ends.

Document US4519559A (Logan) discloses a landing gear of a helicopter landing gear with skids connected to upwardly extending cross tubes pivotably connected to a gas structure. Dampers have a first end that is pivotally connected to the cross tubes and a second end that is pivotally connected to the gas structure. The hydraulic cylinders in the respective dampers are interconnected via hydraulic restoring devices. Computable hydraulic restoration devices force the pistons in each of the hydraulic cylinders to go to the equilibrium position, restoring the length of each landing gear to the equilibrium length after disturbance. Each damper is not suitable for absorbing any vertical energy upon landing of the helicopter. The stiffness to absorb the vertical energy of the landing is provided by the skids and cross tubes of the landing gear of US4519559A. The teachings of US4519559A do not address helicopter ground resonance problems.

It is an object of the present invention to avoid or reduce ground resonance problems caused by helicopter skid type landing gear.

The solution is provided by a helicopter skid type landing gear with the features of claim 1. Preferred embodiments of the invention appear in the dependent claims.

According to the present invention, there is provided a helicopter having a body and a skid type landing gear mounted to the body. The skid-type landing gear comprises cross beams with skids, which are each arranged essentially longitudinally laterally on each side of the longitudinal midplane when the landing gear is raised. Each of the skids is mounted on each side of the longitudinal intermediate surface at at least one side end of the cross beams. Cross beams are designed as support structures for transferring forces and moments between skids and the fuselage. Each of the cross beams is provided with an inner end next to the fuselage. Fixed bearings and floating bearings of the helicopter skid type landing gear of the present invention are provided in the fuselage. Torsion bar springs are provided between the fixed bearings and the floating bearings, in which case the springs of each torsion bar are fixed by at least one of the fixed bearings, and the torsion bar springs are the floating bearings. It is allowed to rotate about their longitudinal axis relative to. The respective inner ends of each cross beam are attached to the torsion bar springs in a floating bearing in such a way that forces and moments are transferred from the respective inner ends of each cross beam to the torsion bar springs, ie the cross beams are pivotable. It is a cantilever cross beam because the cross beam can rotate (turn) to a torsion bar spring mounted against the floating bearing, transferring all of its forces and bending moments to the torsion bar spring. All transverse or any longitudinal forces from the torsion bar springs are supported in the floating bearings. Fixed bearings withstand all moments from torsion bar springs well. At least one separate damper is provided to any of the pivotable cantilever cross beams, wherein the separate damper is connected at one end to each pivotable cantilever cross beam and at the other end to the fuselage. Helicopter skid type landing gear of the present invention meets the above-mentioned rules for energy absorption, FAR / CS-27, FAR / CS-29, while resonating by means of a separate means of elastic deformations and damping of the landing gear. It provides a solution to the problems. The dampers and torsion bar springs of the helicopter skid type landing gear of the present invention are two separate elements that are not automatically aligned. Instead of two cross tubes, the helicopter skid type landing gear of the present invention is provided with four pivotable cantilever cross beams supported in the fuselage on respective torsion bar springs. Through fixed bearings, it is attached at one end of the fuselage structure on a fixed bearing principle to move the torsion moments from the torsion bar springs into the fuselage structure. The torsion bar springs are respectively attached to the pivotable cantilever cross beam via the floating bearing principle for the transfer of forces to the floating bearing and the torsion moments to the torsion bar springs at their opposite ends. The torsion bar springs provide the elastic stiffness of the helicopter skid type landing gear of the present invention in order to absorb the vertical energy upon landing of the helicopter, while at the same time providing a contribution to the elastic stiffness from the cross tubes and skids. Separate dampers, one end of which is connected to the pivotable cantilever cross beams and the other end of which is connected to the fuselage structure, allow for controlled damping of the helicopter skid-type landing gear of the present invention, which separate dampers allow vertical movement during landing of the helicopter. To absorb the energy, it provides a rate dependent energy consumption. The forces acting upon the helicopter of the present invention are separated into two force components, the first of which is completely reversible, acting as a torsion moment in torsion bar springs, and the second component is a damping force. The present invention allows for controlled energy absorption during landing and controllable and adjustable stiffness and damping of the helicopter skid type landing gear behavior of the present invention to avoid ground resonances. Another advantage of the present invention is that by allowing elastic energy absorption, instead of flexible energy absorption, in particular cross-tubes of skid-type landing gears of helicopters usually operated in ships, they soon reach the limits in their setting. This avoids or reduces the regular exchange of routine cross tubes after hard landing, which is an advantage for skid-type helicopters operating on the deck of a ship when they need to be replaced very often. The total weight of the skid type landing gears of the present invention is the same size as the weight of current skid type landing gears. Torsion bar springs and separate dampers of the skid type landing gears of the present invention can be easily replaced when damaged.

According to one preferred embodiment of the invention, the pivotable cantilever cross beams are connected to one end of the torsion bar spring mounted to the floating bearing.

According to another preferred embodiment of the present invention, the pivotable cantilever cross beams on either side of the fuselage are symmetric about the middle plane.

According to another preferred embodiment of the invention, separate dampers are provided with pivotable cantilever cross beams and independent means for attaching to the fuselage.

According to another preferred embodiment of the invention, up to four pivoted cantilever cross beams are attached to four torsion bar springs, in combination with four dampers to flexibly / reversibly absorb the required energies. .

According to still other preferred embodiments of the invention, the at least one separate damper is of adjustable and / or self-adjustable liquid type. The combination of the elastic torsion bar springs and the separate dampers of the skid type landing gears of the present invention allows for fine tuning of the energy absorption by the separate means, and in the design of state of the art skid type landing gears, It is a matter of trial and error and experience / analysis to find the correct stiffness and damping to avoid ground resonances under all possible landing positions.

According to another preferred embodiment of the present invention, two pivotable cantilever cross beams are combined with two dampers on both sides of the fuselage, preferably symmetrical with respect to the midplane of the helicopter, with two torsion bar springs. Is attached to.

Preferred embodiments of the present invention are presented with reference to the following detailed description and drawings.

1 is an isometric view seen from the outside of one side of a skid type landing gear of a helicopter according to the present invention;
2 is a detail of FIG. 1;
3 is another view of FIG.
4 is a cross-sectional view of the floating bearing of the present invention.
5 is a diagram of the redistribution of energy consumed in a skid type landing gear of a helicopter according to the invention.

According to FIG. 1, the left side of the skid type landing gear 10 of the helicopter comprises two aligned torsion bar springs 1. Each torsion bar spring 1 has two ends. The first end is mounted inside the fuselage fitting 6 with a floating bearing 7 integrated about each torsion bar spring 1. The second end of each torsion bar spring 1 is mounted to the body 8 of the helicopter (not shown) by a fixed bearing 9. One torsion bar spring 1 leading through the fixed bearing 9 up to the floating bearings 7 can replace two aligned torsion bar springs 1. The floating bearings 7 face each other with a fixed distance between the fixed bearings 9 and the fixed bearings 9, respectively. The torsion bar springs 1 have an essentially cylindrical cross section. The torsion bar springs 1 are made of metal, such as steel.

Two bow-shaped turning cantilever cross beams 3, 4 are mounted to the torsion bar springs by special means such as a spline (not shown) at each floating bearing 7 to their respective inner ends. do. The two swinging cantilever cross beams 3, 4 are attached at their respective outer side ends, essentially perpendicular to the common skid 5, in which case the swinging cantilever cross beam 3 is attached to the skid 5. It is attached next to the tip.

The cross beams 3, 4 are each arranged essentially in a direction transverse to the main longitudinal axis of the helicopter (not shown). The skids 5 are laterally mounted on each side of the longitudinal intermediate surface when the landing gear 10 is raised, respectively.

The adjustable and / or self regulating liquid type damper 2 has its cylindrical face mounted to the forward pivoting cantilever cross beam 3, and its piston face absorbs the energy transferred from the forward pivoting cantilever cross beam 3 and It is mounted on the fuselage fitting 6 to allow fine adjustments regarding damping to avoid ground resonances. The cantilever cross beam 3 is provided with means such as brackets 11 for attaching said separate damper 2. The orientation of the damper 2 is slightly inclined with respect to the main direction of the turning cantilever cross beam 3.

Another adjustable and / or self-regulating liquid type damper 2 is mounted on its cylindrical face in the rear pivoting cantilever cross beam 4 and its piston face corresponding to the fuselage fitting 6.

According to FIG. 2, corresponding features are referenced with reference to FIG. 1. The torsion bar spring 1 is mounted in a circular opening with gearing of the floating bearing 7. The forward pivoting cantilever cross beam 3 is mounted to the floating bearing 7. The floating bearing 7 is mounted in a fitting 6 attached to the body 8.

The floating bearing 7 is shown in more detail in FIG. 3. The forward pivoting cantilever cross beam 3 is rotatable with the transmission 12 of the floating bearing 7 with respect to the fitting 6. The damper 2 is driven to its cylindrical surface 13 by the forward pivoting cantilever cross beam 3 with respect to the fuselage fitting 6.

According to FIG. 4, corresponding features are referenced with reference to FIGS. 1 to 3. The floating bearing 7 is mounted inside the fitting 6 in an essentially U-shaped rectangular casing 14. The torsion bar spring 1 has roller bearings 15 and 16 mounted inside the coaxial circular openings of the journal-, taper- or fitting 6, and the torsion bar spring 1 Coaxially supported by), the torsion bar spring 1 is coaxially rotatable with the bearings 15, 16.

The swinging cantilever cross beam 3 is provided on the inner circumference of the opening with the transmission 12 and the torsion bar spring 1 is fitted with the transmission 12 on the inner circumference of the swinging cantilever cross beam 3. The bearing is on an outer circumference provided with a coaxial transmission. The torsion bar spring 1 carries the pivoting cantilever cross beam 3 with respect to the fitting 6.

According to FIG. 5, there are two curves, the lower curve for energy absorption in the front cantilever cross beam 3 and the upper curve for energy absorption in the rear cantilever cross beam 4.

The energy absorption in the front cantilever cross beam 3 is approximately 10000 J for a load of 30 to 40 kN and a stroke of 300 to 400 mm at the landing gear 10. The energy absorption in the rear cantilever cross beam 4 is approximately 14000 J for a load of 50 to 60 kN and a stroke of 300 to 400 mm in the landing gear 10.

The Young's modulus of the torsion bar spring 1 is in the range of 200000 N / mm 2 to 220000 N / mm 2 at a Poisson's ratio of about 0.3, and the shear modulus of 80000 N / mm 2 to 81000 N / mm 2 Has a range.

The torsion bar spring 1 is a solid having a length in the range of 900 to 1000 mm and a diameter in the range of 45 to 48 mm. The hollow torsion bar spring 1 has an inner diameter in the range of 40 to 44 mm and an outer diameter in the range of 50 to 54 mm, resulting in a moment of inertia between 440000 mm ⁴ and 480000 mm ⁴ .

The energies elastically absorbed by the torsion bar spring 1 with respect to the front cantilever cross beam 3 correspond to the area under the lower curve EEf. The energies absorbed by the damper 2 with respect to the front cantilever cross beam 3 correspond to the shaded area Def above the lower curve Eef.

The energies elastically absorbed by the torsion bar spring 1 with respect to the rear cantilever cross beam 4 correspond to the area under the upper curve Eer. If the damper 2 is mounted to the rear cantilever cross beam 4, the energies absorbed by the damper 2, relative to the rear cantilever cross beam 4, correspond to the shaded area above the upper curve Eer.

The energies absorbed by the dampers 2 are approximately 5-15% of the energies absorbed by the torsion bar springs 1.

1: torsion bar spring 2: damper
3: cross beam 4: cross beam
5: skid 6: fitting
7: floating bearing 8: fuselage
9: fixed bearing 10: landing gear
11: Bracket 12: Gearing
13: cylindrical face 14: casing
15: bearing 16: bearing

Claims (7)

A helicopter having a fuselage and a skid-type landing gear mounted to the fuselage,
The skid-type landing gear comprises cross beams,
Each of the cross beams is arranged to essentially traverse the longitudinal major axis of the helicopter, the skids of the landing gear are mounted at the side ends of the cross beams,
At least one of the cross beams is provided with an inner end next to the fuselage,
At least one individual damper is provided for said at least one cross beam, one end of said individual damper is connected to said cross beam and another end is connected to said fuselage,
The at least one cross beam is of a pivotable cantilever type,
The fuselage is provided with at least one fixed bearing and at least one floating bearing,
At least one torsion bar spring is supported by the at least one fixed bearing and the at least one floating bearing, and wherein each of the inner ends of the at least one pivotable cantilever cross beam is the at least one pivot The at least one torsion bar spring is attached to the torsion bar spring in the floating bearing in such a way that moments are moved from each inner end of the possible cantilever cross beam to the at least one torsion bar spring. And a torsion bar spring is attached to said fixed bearing in such a way that moments are moved to said fixed bearing. The method of claim 1,
And the at least one pivotable cantilever cross beam is connected to one end of a torsion bar spring mounted to the floating bearing. The method of claim 1,
And the at least one pivotable cantilever cross beam is present on either side of the fuselage. The method of claim 3, wherein
And the pivotable cantilever cross beams present on either side of the fuselage are symmetric about the midplane of the helicopter. The method of claim 1,
And said at least one individual damper is provided with said at least one pivotable cantilever cross beam and independent means for attaching to said fuselage. The method of claim 1,
Wherein said at least one individual damper is adjustable and / or self-regulating liquid-type. The method of claim 1,
And a four pivotable cantilever cross beams attached to four torsion bar springs coupled with four dampers.

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